44 ZOOPHYTES. 



nessed. Like the former, clusters of minute cysts are borne on the head, 

 from which embryos have been obtained in the month of June. The 

 nascent animal is originally white, or of the palest grey — figs. 7, 8. It is 

 so difficult to be obtained, however, that eleven years from the commence- 

 ment of my original observations elapsed before I could procure prolific 

 specimens. The naturalist is compelled to rely on accident as much as on 

 design for the success of his objects. 



The evolution, decay, and disappearance of the head form another 

 illustration of the vigorous reproductive faculty residing in the genus. 

 Here the progressive renewal is more conspicuous than in the preceding, 

 from the readier exposure of the rising embryo, and its stronger contrast 

 with the thin sides of the tubular stem. 



The hydra is deciduous. It survives its fall entire during a certain 

 time, and the summit of the stalk remains vacant. But a florid internal 

 bud is soon discovered ascending towards the extremity of its sno^vy cylin- 

 der, whence it speedily bursts ; and sometimes the progress is so rapid 

 that on one occasion it issued forth and spread, during the course of a 

 single protracted observation. 



In this respect, the Tubidnria larynw probably exceeds the regenera- 

 tions of the indiirim. The limits confining the renovation of these, the 

 parts most essential to life and the perpetuation of its race, cannot be de- 

 fined. 



On April 14, two single specimens were selected for observation — 

 one with eight hydrae, besides several vacant stalks, fig. 2 ; the other with 

 five hydrse and two vacant stalks, or seven summits in all, fig. 3. 



The vacant stalks had flourished recently. Vigorous reproduction 

 now ensued, but attended with much irregularity, both in respect to matu- 

 rity and to its duration, as well as in the number of regenerated organs. 



The specimen, fig. 2, had eight hydrae on the 14th of April, at which 

 time a was vacant. Here a hydra was regenerated on the 20th, which had 

 fallen on the 25th. This hydra was reproduced. I should rather more 

 correctly say, it was succeeded by another next day, the 26th. The last 

 had fallen May 1 ; it was regenerated on the 7th, by one which had fallen 

 on the 12th. Another, regenerated on the 18th, had fallen on the 25th ; 



